Biased hinges

ABSTRACT

A snap-hinge in which two hinge members are hinged together about a first hinge line. A resilient connecting link is joined at one end integrally to one of the hinge members at a second hinge line and is hinged at the other end to the other hinge member at a third hinge line. The connecting link is capable either of compression or of expansion as between its two ends, and tends to maintain the hinge members in a given angular relationship, and to return the hinge members to that relationship if they depart from it.

United States Patent [191 Krawagna )March 20, 1973 [54] BIASED HINGES[75] Inventor: Alois A. Krawagna, Willowdale, On-

tario, Canada [73] Assignee: Western Corporation Toronto, Ontario,Canada [22] Filed: June 17, 1968 [211 Appl. No.: 744,268

Related US. Application Data 7 Limited,

[63] Continuation-impart of Ser. No. 689,390, Dec. 11,

[52] US. Cl ..16/l50, 24/252 [51] Int. Cl. ..E05d 7/00 [58] Field ofSearch ..16/l50;'24/l37 R, 137A, 252 24/252 HC, 252 R; 229/2.5

[56] References Cited UNITED STATES PATENTS 3,289,877 12/1966 Wolf..16/l50 3,292,223 12/1966 Esposito ..24/ 137 Primary ExaminerBemard A.Gelak Assistant Examiner-Doris L. Troutman Att0rney-Thomas T. Rieder[57] ABSTRACT A snap-hinge in which two hinge: members arehingedtogether about a first hinge line. A resilient connecting link is joinedat one end integrally to one of the hinge members at a second hinge lineand is hinged at the other end to the other hinge member at a thirdhinge line. The connecting link is capable either of compression or ofexpansion as between its two ends, and tends to maintain the hingemembers in a given angular relationship, and to return the hinge membersto that relationship if they depart from it.

5 Claims, 22 Drawing Figures PATENTEUMAR20 I975 SHEET 10F 4 P INVENALOIS A. KR'AWAGN PATENT AGENT PATENTEDMARZO I975 3.720.979

SHEET 2 [IF 4 INVENTOR. ALOI S A. KRAWAGNA PATENT AGENT VPATENTEBIMRZOIQYS 3.720379 sum 30F a I N VENTOR ALOIS A. KR WAGNA PATENTAGENT PATENTEUMARZO 1975 3. 720.879 SHEET u 0F 4 138 FIG. 21 134 I N VEN7( )R A OIS AQNA Agent BIASED HINGES This application is acontinuation-in-part of US. application, Ser. No. 689,390, Improvementsin Biased Hinges, filed Dec. 1 1, 1967, Alois A. Krawagna.

This invention relates to biased hinges, or snap-hinges as they aresometimes called, in which the hinge tends to hold itself in a closedposition and/or an open position.

Snap-hinges of the type to which this invention relates include twohinge members hinged to one another, and a biasing member extendingbetween and hinged to both hinge members at points spaced from the hingeline between the hinge members. In accordance with the invention, twobasic types of biasing member can be utilized: the first is a biasingmember adapted to undergo compression as between its two ends; thesecond is a biasing member adapted to undergo expansion as between itstwo ends. With regard to both the compression and the expansion types ofbiasing members, this invention provides that at least one end of thebiasing member be integral with its particular hinge member.

In accordance with one embodiment of this invention, the two hingemembers are pivoted together, and the biasing member is adapted toundergo compression. The biasing member is pivoted to one of the hingemembers but integral with the other. This permits the hinge member withwhich the biasing member is integral to be moulded as a single unitadapted for use with one of a variety of rigid members constituting theother hinge member.

In accordance with the second embodiment of this invention, the twohinge members are integral with one another through a web constitutingthe hinge line about which the hinge members articulate, and the biasingmember is integral with one of the hinge members through a webconstituting a second hinge line, and is integral with the other hingemember at a point constituting a third hinge line, the biasing memberbeing adapted to undergo compression. With this arrangement, thecompression force on the biasing member tends to urge the two hingemembers away from one another when the hinge is articulated. Thisfeature is particularly advantageous in that it places the web portionjoining the two hinge members in tension, and avoids the danger ofshearing which accompanies compression in the web.

In accordance with a third embodiment of this invention, there isprovided a one-piece, integral snap-hinge wherein the biasing memberundergoes expansion, the two hinge members being connected through anintegral web constituting the hinge line about which the hinge membersarticulate. The biasing member has its opposite ends integral with thetwo hinge members through webs constituting further hinge lines. Thefurther hinge lines are spaced from the first hinge line.

In accordance with a fourth embodiment of this invention, there isprovided a snap-hinge in which one of the hinge members consists of twoseparate but interlocking parts. The other hinge member is a one-pieceunit, and the construction of the whole is such that the biasing memberlinks the one-piece hinge member with one part of the other hingemember, and the one-piece hinge member is adapted to engage the otherpart of the other hinge member to hold the two parts firmly ininterlocking engagement with one another. The one piece hinge member canbe removed from engagement with the other part, thereby permitting thetwo parts of the two-part hinge member to be separated completely fromone another.

This invention also provides a method for making by the extrusion methoda snap-hinge: in which the biasing member undergoes expansion.

Specifically, this invention provides a snap-hinge, comprising: a firsthinge member, a second hinge member hinged to said first hinge memberabout a first hinge line, a resilient connecting link joined at one end1 integrally to said first hinge member at a second hinge line andhinged at the other end to said second hinge member at a third hingeline, the resilient connecting link tending resiliently to maintain itstwo ends apart at a given spacing, said second hinge line being spacedat an invariable distance from said first hinge line, said third hingeline being spaced at an invariable distance from said first hinge line,the snap-hinge having a position in which stress in the connecting linkis at a minimum, the snap-hinge being at rest in said position, a smalldeparture from which increases the stress in the connecting link, whichtends to restore the snap-hinge to said position.

The embodiments of this invention are shown in the accompanyingdrawings, in which like numerals denote like parts throughout theseveral views, and in which:

FIG. 1 is a perspective view of one embodiment of this invention;

FIG. 2 is a sectional view taken along the line 2-2 in FIG. 1;

FIG. 3 is a sectional view of the hinge shown in FIG. 2, with one hingemember hinged to an intermediate position with respect to the otherhinge member;

FIG. 4 is a sectional view of the hinge shown in FIGS. 2 and 3, with thehinge members closed together;

FIG. 5 is a perspective view of the second embodiment of this invention;

FIG. 6 is a sectional view taken at the line 6-6 in FIG. 5;

FIG. 7 is a sectional view of the hinge shown in FIG. 5, with the hingemembers closed against one another;

FIGS. 8 and 9 show two modifications of the second embodiment of thisinvention;

FIG. 10 is a perspective view of one form of the third embodiment ofthis invention;

FIG. 11 is a frontal view of the embodiment shown in FIG. 10;

FIG. 12 is an elevational view of an extruded form of the thirdembodiment of this invention;

FIG. 13 is a cross-sectional view of the extruded third embodiment shownin FIG. 12;

FIG. 14 is a view similar to FIG. 13, showing the two hinge members atan intermediate angular position;

FIG. 15 is a view similar to FIGS. 13 and 14, showing the two hingemembers closed against one another;

FIG. 16 is a perspective view of a special form of the first embodimentof this invention;

FIG. 17 is a perspective view of one variant of the fourth embodiment ofthis invention, showing the two portions of the two-part hinge member inspaced relation;

FIG. 18 is a vertical, longitudinal sectional view of the embodimentshown in FIG. 17, with the two portions of the two-part hinge memberengaged with one another;

FIG. 19 is a view similar to FIG. 18, showing the locking hinge memberat its balance point, about to be urged to the over-toggled lockingposition;

FIG. is a view similar to FIGS. 18 and 19, showing the locking hingemember in the locked position;

FIG. 21 is an elevational view of another variant of the fourthembodiment of this invention, wherein the biasing member is bowed inorder to increase its capacity for expansion; and

FIG. 22 is a perspective view of the variant shown in FIG. 21.

FIG. 1 shows a hinge 10, generally comprising a first hinge member 11and a second hinge member 12. The first hinge member 1 1 has twoparallel arms 14 extending leftwardly from the hinge member 11, the arms14 being rigid with respect to the hinge member 11. The second hingemember 12 has two rightwardly protruding appendages 16, which are rigidwith respect to the hinge member 12. The arms 14 each carry a pivot pin17 (only one visible in FIG. 1) by which the arms 14 are pivoted to theappendages 16. Thus, the second hinge member 12 is hinged to the firsthinge member 11 about a first hinge line 18, which constitutes thecommon axis of the pins 17. The first hinge member 11 has a resilientconnecting link 20 integral therewith between the arms 14, and extendingleftwardly toward the second hinge member 12. It will be noted that thelocation 22 at which the resilient connecting link 20 is integral withthe hinge member 11 is spaced from the first hinge line 18.

The resilient connecting link 20 has a pin 24 passing therethrough atits left-hand end, and the ends of the pin 24 are pivoted to theappendages 16 at a location spaced from the first hinge line 18. Theaxis of the pin 24 constitutes a second hinge line 26. It is essentialto this invention that the first and second hinge lines 18 and 26 bespaced rigidly from one another.

Turning now to FIG. 2, it will be seen that the righthand end of theconnecting link 20 is rigidly integral with the first hinge member 11,sincethe connecting link 20 does not decrease in thickness to form aflexible web where it joins the hinge member 11. By comparison, a glanceat FIGS. 8 and 9 shows the connecting link to be hingedly integral withthe hinge member, due to the flexible web portion connecting them.

Returning to FIG. 2, it is assumed here that the position of the hingemembers 11 and 12 shown is the normal at-rest open position for thehinge, with the hinge members being 180 apart. In this position, theconnecting link 20 is subject to the least compression bowing stress ofany position between FIG. 2 and FIG. 4. If the first hinge member 11 isformed with the integral connecting link originally parallel with thearm members 14, some bowing stress will be introduced into the link 20when its left-hand end is raised and pivoted to the appendages 16 alongthe second hinge line 26. Alternatively, the first hinge member 11 canbe formed with the resilient connecting link 20 already in the slightlycurved configuration shown in FIG. 2. It will be noted that the arms 14and the hinge member 11 are considerably thicker in the verticaldirection than is the connecting link 20. The purpose of the relativedifference in thicknesses is to make the connecting link 20 a relativelyresilient or bendable member, as compared to the more rigid hinge member11 and arms 14, even though the hinge member 11, the arms 14 and theconnecting link 20 are all formed of the same material.

As the first hinge member 11 begins to pivot in the counter-clockwisedirection with respect to the second hinge member 12, it will be obviousthat, due to the spacing between the hinge lines 18 and 26, the ends ofthe resilient connecting link 20 will be urged together to place thelink in compression, and the result will be a compression bowing in theconnecting link 20.

FIG. 3 shows the bowing of the resilient connecting link 20 at itsmaximum, and this is determined by the alignment of the hinge lines 18and 26 and the point 28, which can be considered the approximate pointof attachment between the resilient connecting link 20 and the firsthinge member 11. The geometry of the system is such that the two ends ofthe resilient connecting link 20 are closest when the point 28 is linedup with the hinge lines 18 and 26. The amount by which the rectilineardistance between the ends of the connecting link is shortened in FIG. 3is shown as D. As the first hinge member 11 moves leftwardly in thecounterclockwise direction past the FIG. 3 position, the resilientconnecting link 20 begins to straighten out, but it is still notcompletely relieved of compression bowing stress when the hinge members11 and 12 have closed upon one another. The reason for this is the factthat the hinge line 26 is slightly to the left of the hinge line 18.Explanations of this intentional residual compression spring loading andother angular travel relationships are contained in later paragraphs.

Returning to FIG. 2, it will be appreciated that, because the hinge line26 is spaced upwardly from the hinge line 18, as soon as the hingemember 11 begins to pivot in the counter-clockwise direction above thehinge line 18 and compress the resilient connecting link 20, the latterwill exert a force on the first hinge member 11 tending to return it tothe FIG. 2 position. The torque T tending to return the first hingemember 11 to its FIG. 2 position will be given by the relationship:

T= FL (sin :1)

where L is the distance between the hinge line 18 and the point 28, F isthe compressive force exerted on the resilient connecting link 20, andd) is the angle in the vertical plane subtended at the point 28 by thehinge lines 18 and 25. The angle d) is shown in FIG. 2.

It will be appreciated that, when the first hinge member 11 has reachedthe FIG. 3 position, where the point 28 is lined up with the hinge lines18 and 26, the angle 4: drops to zero, and the restoring torque Tlikewise drops to zero. Thus, when the hinge is in the FIG. 3 position,it is in a condition of unstable equilibrium. As the first hinge member11 moves past the FIG. 3 position in the counter-clockwise direction,the angle d increases from zero to a finite value, and causes a torquein the counter-clockwise direction which is also given by the expressionabove. Because the resilient connecting link 20 is still under somecompression in the FIG. 4 position, the hinge members 11 and 12 areurged together in the FIG. 4 position.

It will be appreciated that the second hinge member 12 need not be inthe exact shape shown, since its sole function is to provide connectingportions for the pivot pins 17 and 24.

Turning now to FIG. 5, which shows the second embodiment of thisinvention, it will be seen that a hinge shown generally at 30 comprisesa first hinge member 31 and a second hinge member 32. The first hingemember 31 has two arm members 33 extending toward the second hingemember 32, and each of the arm members 33 is integral, at its left-handend, with the second hinge member 32 through a web 34, the thin centralportion of which defines a first hinge line 36. Between the two webs 34,the second hinge member 32 has a rigid upstanding extension 38, of whichthe upper portion is integral through a web 40 with the left-hand end ofa resilient connecting link 42, of which the righthand end is rigidlyintegral with the first hinge member 31, as best seen in FIG. 6. The web40 defines a second hinge line 44, and the point 45 is the approximatepoint of attachment between the link 42 and the member 31. The sameexpression for the opening or closing torque T applies for thisembodiment as for the embodiment shown in FIGS. 1 to 4. The secondembodiment of the hinge has not been shown in a position similar to FIG.3, since the same configuration would result and the geometricconsiderations would be the same. FIG. '7 shows the second embodiment inthe position corresponding to FIG. 4 for the first embodiment, and itwill be appreciated again that, since the second hinge line 44 islocated slightly to the left of the first hinge line 36, the resilientconnecting link 42 is still under some compression in the FIG. 7position, and thus there will be a force tending to urge the hingemembers 31 and 32 together in the FIG. 7 position.

In this second embodiment, it will be appreciated that the action of theresilient connecting link 42 is at all times to place the web 34 intension. This is an advantage because if the web 34 were in compression,there would be a danger of overlapping and shearing with repeatedflexings.

FIGS. 8 and 9 show alternative designs for the resilient connecting link42. In FIG. 8, the link 42 is slightly bowed concave upwardly in itsunstressed position, and there is a web 50 at the right-hand end as wellas a web 51 at the left-hand end where the link 42 joins the projection38. FIG. 9 is similar to FIG. 8, except that the resilient connectinglink is convex upwardly in its unstressed condition. Again, there is aweb 50 at the right'hand end of the link 42, with a web 51 at thelefthand end.

In the discussion that follows the snap-hinges shown in FIGS. 1 through9 will be considered to have three parallel bending lines: line A,representing the lines 18 and 36; line B, representing the lines 28 and45; and line C, representing the lines 26 and 44. The letters A, B and Care shown in FIGS. 2 and 6. For purposes of this description, bendinglines A and B are located in the same initial horizontal plane. Aspointed out earlier, the location of bending line C to the left ofbending line A results in residual compressive stress in the resilientconnecting link when the hinge is in the closed position, becausemechanical interference between the first and the second hinge memberprohibits rotation of the first hinge member to the other location ofcompletely relieved compression bowing stress. The obvious advantage ofclamping closure force between the hinge members results. FIGS. 4 and 7illustrate this condition of rotation, mechanically stopped at 180travel of the first hinge member.

It will be further realized that as bending line C is angularlydisplaced in the counter-clockwise direction, with bending lines A and Bstill in the same horizontal plane, a configuration will be arrived atwherein the first hinge member reaches closure (mechanical interference)just as the bending lines A, C and B become aligned (angle 4: zero).This configuration will be determined by the initial angulation of thehinge members and the location of the bending line C. These conditionsdescribe an always open" compression hinge. Another way of putting it isto say that the first hinge member, because of mechanical interference,never goes beyond a position of unstable equilibrium.

Still further analysis of the positional relationship of the bendinglines contemplated by this invention reveals that as bending line Cmoves clockwise and goes to the right of the vertical at the bendingline A, it is possible to select specific values of angular travelbetween 0 and 180 for the first hinge member. Also, as C movescounter-clockwise to the left with respect to the vertical at bendingline A, unstopped angular travel of the first hinge member will begreater than 180 and specific values between H and 360 may be selected.Unstopped angular travel is a hypothetical situation in which nomechanical interference between the two hinge members takes place.Bending line C, it will be noted, is always located on the bisector ofthe angle describing unstopped first hinge member travel. Assuming themoment of inertia and the modulus of elasticity of the connecting linkto be known, spring force may also be computed.

It will thus be appreciated that, when the snap-hinge is formed inmanufacture with the hinge members at a designated angular relationship,and rotation of the first hinge member is intended to bring the twohinge members together, it is possible to provide a predeterminedclosure force to be exerted by the connecting arm, by selecting theappropriate material and dimensions for the latter. Also, when the hingemembers are formed at a designated angular relationship and rotation ofthe first hinge member brings it to only a portion of the initialangulation before it reaches an at-rest position, a determination ofthis second at-rest position can be made.

Those skilled in the art will appreciatethat in the event the two hingemembers are formed with an angular relationship less than approximately30 or more than 330, certain manufacturing complexities will beencountered in the webbed embodiment. Further, an initial angularrelationship approaching zero as the limit is of little or no value asfar as the purposes of this invention are concerned.

Turning now to FIGS. 10 and 1.1, there is shown one form of a thirdembodiment of this invention, in which the connecting link is adapted toundergo expansion as between its two ends. The hinge shown in FIGS. 10and 11 is adapted for use with pipe insulation, which is usuallyavailable as two semi-cylindrical portions adapted to be clampedtogether around the pipe. Sometimes the two portions of insulation arejoined along one edge by an outer skin bridging between the portions,such that the portions can hinge about that point. In other cases, thetwo portions are made separately, without any connection or hinge meansbetween them. The hinge device shown in FIGS. 10 and 11 is adapted to beinserted into one end of a length of split insulation, with two prongs52 and 53 inserted into one portion of the insulation and two prongs 54and 55 inserted into the other portion thereof. The prongs 52 and 53project integrally from a first hinge member 57, while the prongs 54 and55 project integrally from a second hinge member 58. As best seen inFIG. 11, the two hinge members 57 and 58 are integral with one anotherthrough a flexible web 60, which is considered to constitute a firsthinge line. Both hinge members 57 and 58 are moulded with across-section in the shape of a T, in order to give rigidity to themembers 57 and 58. The prongs 52-55 are slightly tapered and pointed,for ease of insertion into the insulation material, which is usuallyeither fiberglass or cellular plastic. A connecting link 62 of circularconfiguration is joined integrally at one end to the hinge member 57through an integral web 64 constituting a second hinge line, and isjoined at the other end to the second hinge member 58 through a furtherintegral web 66 constituting a third hinge line. The connecting link 62has, as shown in FIG. 10, a roughly triangular cross-section, althoughthis is not essential.

The position of the snap-hinge of FIG. with respect to the split pipeinsulation with which it is used is shown in FIG. 11, in which the pipeinsulation has been shown in broken lines. The snap-hinge is positionedwith the web 60 lying adjacent the intersection of the outer periphery67 of the pipe insulation and the split line 68 between the two portions69 and 70 of the pipe insulation. The prongs 5255 are symmetricallyarranged with respect to the split line 68, and inserted into theinsulation material. The snap-hinge thus acts as a hinge between the twoportions 69 and 70, which articulate about the web 60, while theconnecting link 62 serves as a spring tending to maintain the twoportions 69 and 70 in their closed position (that shown in broken linesin FIG. 1 l

If it were desired to have a positive closure force exerted on theportions 69 and 70 when they are in the closed position, the hingemembers 57 and 58 would be spread apart to some extent before insertionof the prongs 52-55, such that the rectilinear distance between theprongs 52 and 55 is greater than the distance between them in theunstressed condition.

If the two portions 69 and 70 of the pipe insulation, with the prongedsnap-hinge of FIG. 10 inserted in one end as described above, were nowto be gradually spread apart, articulating about the web 60, theconnecting link 62 would be resiliently expanded, and would try to urgethe two portions back together. If, however, the two portions 69 and 70were spread far enough apart that the prongs 52, 53, 54 and 55 werebrought into line with one another, the force exerted by the connectinglink 62 would no longer urge the portions 69 and 70 together, since thesnap-hinge would be in a state of unstable equilibrium. If the portions69 and 70 were expanded beyond the position in which unstableequilibrium occurs, the connecting link 62 would urge the portions 69and 70 toward an open position.

Thus, by applying a snap-hinge of the type shown in FIG. 10 to the endof a length of split pipe insulation (or two: one at either end), thelength of split pipe insulation would have a hold-closed and a hold-openposition.

FIG. 13 shows, in cross-section, an extruded form of the thirdembodiment of this invention. The cross-section of the extrudate showngenerally at 72 in FIG. 13 is composed of two opposed portions 73 and 74joined by a relatively thin portion 75 constituting a first web in theextrudate. A curved portion 76 is joined to both of the opposed portions73 and 74 at points spaced from the first web 75. The curved portion 76is joined to the portion 73 through a thin portion 78 constituting asecond web in the extrudate, and is joined to the portion 74 through athin portion 80 constituting a third web in the extrudate. The curvedportion 76 lies to one side of the hypothetical line 81 joining thesecond web 78 and the third web 80. The first web 75 lies on the otherside of the hypothetical line 81 and is spaced therefrom. Thecharacteristics described above are essential to a hold'open,hold-closed extruded snap-hinge in which the connecting link undergoesexpansion. As can be seen, the curved portion 76 has a circularcurvature, although this is not essential. What is essential is that thestraightened length of the curved portion 76 be at least as long as thesum of the rectilinear distance between the first web 75 and the secondweb 78 plus the rectilinear distance between the first web 75 and thethird web 80. Otherwise the hinge would not be a snap-hinge, because thecurved portion 76 would be incapable of sufficient expansion to permitthe first, second and third webs 75, 78 and 80 to become aligned. Itwill be understood that this position of alignment will constitute thestate of unstable equilibrium for the snap-hinge, without which thehinge would be able to maintain only one position. The straightenedlength of the curved portion 76 will lie somewhere between the length ofthe inside are 82 and the length of the outside are 83.

FIGS. 14 and 15 show the extruded snap-hinge in, respectively, anintermediate hinged position, and the closed position in which theportions 73 and 74 are closed against one another. It will be notedthat, in FIG.

' 14, the curved portion 76 is expanded to a radius of curvature greaterthan that which it has in either FIG. 13 or FIG. 15.

The opposed portions 73 and 74 are each equipped with a slot 84 capableof receiving and gripping an appropriate plate-like element, the twoplate-like elements so gripped being snap-hinged together by theextruded snap-hinge about the web 75.

The method according to this invention involves the steps of extrudingan integral extrudate from stiff but resilient material such aspolypropylene, which extrudate has a cross-section meeting the criteriaset out above, and cutting the extrudate transversely to obtain asection thereof.

FIG. 16 shows a special form of the first embodiment of this invention.Only the first hinge member 86 is shown. The hinge member 86 has twospaced-apart arms 87 supporting outwardly projecting pivot pins 88 attheir extremities. Between the arms 87 is a connecting link 90 which hastwo opposed, aligned pivot pins 91 at its end. The connecting link 90 isthinner than the arms 87, such that the connecting link 90 is resilientby comparison with the arms 87. The hinge member 86 is adapted to bepivotally connected to another rigid hinge member (not shown) throughthe pivot pins 88, the common axis of which constitutes the firstbending line A. The connecting link 90 is also adapted to be pivotallyconnected to the other rigid hinge member through the pivot pins 91, thecommon axis of which constitutes the third bending line C. The line B inFIG. 16 represents the approximate point of attachment between theconnecting link 90 and the hinge member 86 and is considered to be thesecond bending line of the hinge. In the at-rest position the lines A, Band C are in alignment, with A intermediate B and C. This arrangementgives a 360 hinge configuration, in which the connecting link 90 beginsto undergo compression as soon as the hinge member86 begins to pivotwith respect to the other hinge member, regardless of the direction ofpivoting. It will be appreciated that this hinge configuration has onlyone at-rest position, and that the position of unstable equilibriumarises at 180 displacement from the atrest position.

Turning now to FIG. 17, the first variant of the fourth embodiment ofthis invention is seen to include a first hinge member 94, a splitbiasing member consisting of two portions 95a and 95b, and a secondhinge member consisting of a first part 96 and a second part 98. In oneapplication of the fourth embodiment of this invention, the parts 96 and98 constitute, respectively, the two free ends of a split sealing ringadapted to close the periphery of tape reels against the entry of dustand other foreign material. These sealing rings, and the tape reels withwhich they are used, are widely employed in the data-processing field.Thus, while the following description assumes that the parts 96 and 98are distinct, separate items, this does not preclude an arrangementwherein the two parts are linked remotely, as in a circular sealing ringof the above type.

Attention is now directed specifically to the part 96, which consists ofa base portion 100, and a surmounting portion 102. The base portion 100is a flat, bandlike, elongated element having two parallel grooves 104which are adapted to receive the peripheries of the two circular platesconstituting a tape reel (not shown). The surmounting portion 102 can beeither formed integrally with the base portion 100, or affixed theretoby some other conventional means, such as glueing, welding, ormechanical attachment. The surmounting portion 102 consists essentiallyof a block-like element 105 to which the portions 95a and 95b of thebiasing element are hingedly connected along integral webs 106 which arecollinear. As is evident in FIG. 17, the two portions 95a and 95b of thebiasing element are spaced apart, and the block-like element 105 has,between the portions 95a and 95b, a groove 108 of which the purpose willpresently be explained.

The part 98 consists of a base portion 110 which is identical incross-section to the base portion 100 of the part 96, surmounted by alocking element 112. Again, the locking element 112 can be either formedintegrally with the base portion 110, or affixed thereto by means ofglue, welding, mechanical attachment, etc. The locking element 112consists of a lower portion 114, and an upstanding portion 116. Thebreadth of the upstanding element 116 is less than the lateral distancebetween the portions 95a and 95b of the biasing element, such that theportions 95a and 95b can lie on either side of the upstanding portion116. The portion 116 defines a groove 117 opening remotely from the part96. Integral with the upstanding portion 116 is a horizontalprotuberance 118 which is adapted for complementary engagement with thegroove 108.

It will be appreciated that, while in the embodiment shown, the baseportions 100 and 110 have identical cross-sections, this is due merelyto the particular application of the fourth embodiment to the two freeends of a split sealing ring. Obviously, the base portions 100 and 110could be replaced with any other abutting members.

The first hinge member 94 has a tongue 120 extending therefrom betweenthe portions a and 95b of the biasing element.

FIGS. 18 to 20 show sequential steps in the operation of locking the twoparts 96 and 98 together by means of the biased hinge. FIG. 18 shows thetwo base portions and abutting one another, with the protuberance 118lodged in the groove 108. When this complementary abutment has takenplace, it is then possible to swing the first hinge member 94 downwardlyso that the end 121 of the tongue projecting from the hinge member 94can lodge inside the groove 117 to create a hinge axis between the firsthinge member 94 and the part 98 of the second hinge member. It isconsidered that the two parts 96 and 98 of the second hinge member canbetaken as a single member when they are in the abutting relationshipshown in FIGS. 18 to 20. Thus, it is permissible to speak of a hingingrelation between the first hinge member 94 and the second hinge member(parts 96 and 98) when the tongue 120 is lodged in the groove 117.

FIG. 19 shows the first hinge member 94 after it has been rotated in theclockwise direction to the point of unstable equilibrium, which ariseswhen the two points 123 and 124, representing the hinge lines alongwhich the biasing element 95 is attached to the surmounting portion 102and to the first hinge member 94 respectively, are aligned with thepoint 126, the latter representing the line along which the tongue 120bears against the surface of the groove 117, thereby defining aninstantaneous axis of rotation of the first hinge member 94 with respectto the second hinge member comprising parts 96 and 98.

The design of the biasing portions 95a and 95b is such that they are ina state of longitudinal tension in the over-toggling position ofunstable equilibrium shown in FIG. 19. Although actual stretching in thebiasing portions 95a and 95b is minimal, the integral web connectionbetween the biasing portions 95a and 95b and both the surmountingportion 102 and the first hinge member 94 will stretch or deform to alarger degree. It is important, of course, so to design the biasingmembers 95a and 95b that the webs aforementioned will not be stretchedto rupture.

Further clockwise rotation of the hinge member 94 with respect to thecomposite hinge member comprising parts 96 and 98 will bring the firsthinge member 94 to the FIG. 20 position, in which the hypothetical linejoining points 123 and 124 has gone past the point 126. It will beapparentthat, in the FIG. 20 position, the stress in the biasingportions 95a: and 95b will be less than in the FIG. 19 position, andthis situation will en- I sure that the first hinge member 94 remainsbiased to the FIG. 20 position. Thus, the residual tension in thebiasing portions 950 and 95b will hold the two parts 96 and 98 in atightly abutting relationship.

Another variant of the fourth embodiment of this invention is shown inFIGS. 21 and 22, in which it will be noted that the two portions 130aand 13% of the biasing element 130 are curved in the vertical plane. Theother elements are similar to those of FIGS. 17 to 20, and include afirst hinge member 131, a second hinge member consisting of a first part133 and a second part 134, the part 134 being affixed to or integralwith a grooved portion 136 which has a first groove 137 in which therounded end 138 of the first part 133 is adapted to lodge, and a secondgroove 140 in which the tongue 142 of the first hinge member 131 isadapted to be received. It will be appreciated that the curved biasingportions 130a and 13% are capable of absorbing a greater deflectionunder tension than is the case with the straight biasing portions 95aand 95b in FIGS. 17 to 20. For this reason, the dimensional designcriteria in the variant shown in FIGS. 21 and 22 are not so critical.

In the variant shown in FIGS. 17 to 20, the hinge axis denoted by thepoint 126 is analogous to the hinge represented by the web 75 in FIG.13, the hinge axis denoted by the point 124 is analogous to the hingerepresented by the web 78 in FIG. 13, and the hinge axis denoted by thepoint 123 is analogous to the hinge represented by the web 80 in FIG.13.

It will be evident that the same over-toggling considerations hold forthe second variant shown in FIGS. 21 and 22 as for the first variantshown in FIGS. 17 to 20. It is not considered necessary to show thehinge axes in the second variant of the fourth embodiment.

It will be appreciated that the fourth embodiment of this inventionlends itself to integral moulding techniques, such that the element 112could be moulded integrally with the second part 98, and such that thefirst hinge member 94, the biasing portions 95a and 95b and thesurmounting portion 102 could all be formed integrally with the firstpart 96.

In the appended claims, the word hinged is intended to cover both anintegral web hinge and a hinge employing a pivot pin. The word pivotedis to be construed as covering only those hinge arrangements in whichsome sort of pivot pin is utilized. Pivoted does not include an integralweb hinge. The term hingedly integral describes the flexible webconnection which is shown in FIGS. 8 and 9 between the connecting link42 and both hinge members. The term rigidly integral" describes thenon-flexible connection which is shown in FIG. 2 between the connectinglink and the first hinge member 1 1.

While preferred embodiments of this invention have been disclosedherein, those skilled in the art will appreciate that changes andmodifications may be made therein without departing from the spirit andscope of this invention as defined in the appended claims.

What I claim as my invention is:

1. A snap-hinge comprising:

a first hinge member,

a second hinge member hinged to said first hinge member about a firsthinge line,

a curved resilient connecting link of uniform crosssection joined at oneend integrally to said first hin'ge member at a second hinge line andjoined at the other end integrally to said second hinge member at athird hinge line, the resilient connecting link tending resiliently tomaintain its two ends apart at a given spacing, said second hinge linebeing spaced at an invariable distance from said first hinge line, saidthird hinge line being spaced at an invariable distance from said firsthinge line, the snap-hinge having a first position and a secondposition, in each of which stress in the connecting link is at aminimum, the snap-hinge being at rest in each of said positions, a smalldeparture from either of which increases the stress in the connectinglink, which tends to restore the snap-hinge to the respective position,the connecting link being capable of resilient expansion between its oneend and its other end, the snap-hinge being adapted to articulatebetween said first-mentioned position and said second position in such away that the connecting link is resiliently expanded in positionsintermediate said first-mentioned position and said second position, themaximum expansion of said connecting link representing a state ofunstable equilibrium for the snap-hinge, departure from which in eitherdirection causes said connecting link to urge the snap-hinge further inthat direction to return the snap-hinge to one of said positions.

2. A snap-hinge as claimed in claim 1, in which said second hinge lineand said third hinge line are equidistant from said first hinge line.

3. A snap-hinge as claimed in claim 1, in which said first hinge memberis integral with said second hinge member through a flexible webdefining said first hinge line, in which said one end of said resilientconnecting link is integral with said first hinge member through aflexible web defining said second hinge line, and in which said otherend of said resilient connecting link is integral with said second hingemember through a flexible web defining said third hinge line.

4. A snap-hinge as claimed in claim 3, in which said first and secondhinge members and said resilient connecting link are made of athermoplastic material.

5. A snap-hinge as claimed in claim 4, in which said thermoplasticmaterial is polypropylene.

l 0' t I t

1. A snap-hinge comprising: a first hinge member, a second hinge memberhinged to said first hinge member about a first hinge line, a curvedresilient connecting link of uniform cross-section joined at one endintegrally to said first hinge member at a second hinge line and joinedat the other end integrally to said second hinge member at a third hingeline, the resilient connecting link tending resiliently to maintain itstwo ends apart at a given spacing, said second hinge line being spacedat an invariable distance from said first hinge line, said third hingeline being spaced at an invariable distance from said first hinge line,the snap-hinge having a first position and a second position, in each ofwhich stress in the connecting link is at a minimum, the snap-hingebeing at rest in each of said positions, a small departure from eitherof which increases the stress in the connecting link, which tends torestore the snap-hinge to the respective position, the connecting linkbeing capable of resilient expansion between its one end and its otherend, the snap-hinge being adapted to articulate between saidfirst-mentioned position and said second position in such a way that theconnecting link is resiliently expanded in positions intermediate saidfirstmentioned position and said second position, the maximum expansionof said connecting link representing a state of unstable equilibrium forthe snap-hinge, departure from which in either direction causes saidconnecting link to urge the snap-hinge further in that direction toreturn the snap-hinge to one of said positions.
 2. A snap-hinge asclaimed in claim 1, in which said second hinge line and said third hingeline are equidistant from said first hinge line.
 3. A snap-hinge asclaimed in claim 1, in which said first hinge member is integral withsaid second hinge member through a flexible web defining said firsthinge line, in which said one end of said resilient connecting link isintegral with said first hinge member through a flexible web definingsaid second hinge line, and in which said other end of said resilientconnecting link is integral with said second hinge member through aflexible web defining said third hinge line.
 4. A snap-hinge as claimedin claim 3, in which said first and second hinge members and saidresilient connecting link are made of a thermoplastic material.
 5. Asnap-hinge as claimed in claim 4, in which said thermoplastic materialis polypropylene.